Tag Archives: duramax

Pickuptrucks.com has once again held a competition pitting the Big 3 automakers against eachother in a test to see who comes out on top. This particular test, aptly named ‘Heavy Duty Hurt Locker’ had one-ton dual rear wheel pickups complete a 2,200 mile journey across 4 states through 2 of the most gruelling mountain climbs in North America. The trucks pulled gooseneck trailers weighing nearly 10 tons through the journey (meaning a commercial drivers license was required!) and were evaluated on their fuel economy, power, acceleration and braking. Trucks were also measured on closed courses, going full throttle with and without trailers, to measure their performance at 100% power capability.

The trucks all fared well and had their own pro’s and con’s in each test, but in the end the award was given to the GMC Sierra 3500, with the writers stating:

The GMC Sierra 3500 is our choice for the Best Overall Heavy-Duty Truck in the Hurt Locker test. Its performance continues to affirm what we’ve seen from previous 2011-12 GM HD pickups. Their chassis and on-road performance should be in the crosshairs of Ram and Ford.

The GMC Sierra led with best-in-class performance, with wins in almost every test we put the trucks through.

The Sierra was the most comfortable rig over our long days. It was also the quickest for the driver to get comfortable with the trailer and load.

Pickuptrucks.com recently held a competition between the new GM and Ford one-ton HD trucks called the Rumble in the Rockies, pitting the trucks against eachother on the “Nurburgring of Pickups” at the Eisenhower Pass in Colorado. After their Heavy Duty Shootout over the summer, there was backlash over the short test distances as well as the newer available engine option from Ford that ups its power and torque numbers, so the Rumble in the Rockies was their final test to really find the true best truck between the GM and Ford. The two trucks used were about as apples-to-apples as you can get, with a $65 price differential, and a few lbs. difference in the GCWR – the GM was a Chevy Silverado LT 3500HD DRW 4×4 with a 6.6L Duramax, while the Ford was an F-350 XLT DRW 4×4 with a 6.7L Power Stroke with the Job 2 option of 400 hp and 800 lb. ft of torque.

This competition was done solely by a third party (pickuptrucks.com paid for their own accomodations and for all the testing) to keep any calls for purposefully schewing the numbers, after GM had challenged Ford to a real-world showdown in the Rockies but Ford declined the invitation.

The Eisenhower Pass is an extremely difficult stretch of road to encounter will pulling a loaded trailer, as basically every bit of towing and braking hardware is stressed at a very high altitude for multiple miles at a time – so what better place to stage the competition? The grade starts at 5% for 2 miles, and increases to 7% for the remaining 6 miles until the entrance of the Eisenhower Tunnel – which is the highest tunnel in the US. The trucks pulled a 6,500 lb gooseneck trailer loaded with three 4,140 lb pallets for a total of 18,920 lbs. over that stretch – this brought the total GCWR to 27,940 lbs for the Chevy and 28,160 lbs for the slightly heavier Ford.

The first part of the test ran the trucks 7.6 miles up the pass, rising 2,224 feet over that distance, before coming back down and evaluating the exhaust brakes on the way down. You can check the full article for the in-depth analysis of each run, but for our purposes I’ll just give a quick rundown: The Ford ran 4 times, starting in 4 wheel drive and switching to 2 wheel drive at approximately 30 mph, and only 3 adult males were present in the truck on the first 2 runs to offset the Chevy’s 220 lb curb weight advantage (as the article points out, 220 lbs is basically unnoticable when you’re moving 15 tons uphill.) The best run the Ford could muster was 10 minutes, 46.8 seconds with an average speed of 42.41 mph and a top speed of 58.5 mph.

Next up was the Silverado’s turn, using the same parameters as the Ford, and the Chevy was significantly faster – finsihing in 8 minutes, 38.2 seconds – more than 2 full minutes quicker than the F-350! The average and top speed of the Chevy was also higher, at 53.63 mph and 67.38 mph respectively.

The next test was the exhaust brake, bringing that 15 tons back down the pass on a white knuckle stretch of highway while trying to keep the trailer and truck controlled. The big difference between these 2 trucks being that the Silverado has a push-button activated exhaust brake, while the Ford’s exhaust brake is automatically enabled whenever the truck is in Tow/Haul and can’t be turned off by the driver.

The difference in exhaust brake performance (echoing the must shorter test performed in the HD Shootout) was starker than the difference towing up the hill

In the test, they wanted to see which truck required the least amount of wheel brake application, so when speeds reached 60 mph, the driver applied his left foot to the brake to slow down the truck to 52 mph to start the cycle again. Through four runs, the Ford had to be manually slowed down 11 to 14 times during each descent, with the exhaust brake seeiming to have minimal effect. On the other hand, the Chevy, as pickuptrucks.com but it, was a “Superhero on the descent” with an average of only one to two manual brake applies on each run. The most telling aspect of the run was at the turnaround point at the bottom of the pass, where you could smell the hard-worked brakes on the Ford, but nothing coming from the Chevy.

As you can see from the results, the Chevy was the clear winner in the performance categories tested during the Rumble in the Rockies, and is the top choice among the writers over at Pickuptrucks.com for new HD pickups. As they put it:

There’s no question that GM’s latest diesel pickups are the performance leaders in the class. Chevy doesnt just run deep. It runs high as well.

Couldn’t have said it better myself.

**Thanks to Pickuptrucks.com for the info on the test, head over to their site for great in-depth views into the full test**

Pickuptrucks.com is reporting that GMC is going to unveil a preview of its next generation Sierra HD at the North American International Auto Show in Detroit in January. For the 2011 model, GM introduced an all new chassis and an updated Duramax diesel V8 engine, but the body style has remained the same since its mid-2007 model year launch. More news to come when GM officially announces the concept, we’re looking forward to it!

GM has recently announced the power ratings for the 2011 Duramax Diesel V8, and its up – WAY up. The 2011 Duramax will have 397 hp and a whopping 765 lb.-ft. of torque, up 32 hp and 105 lb.-ft. from the previous Duramax. As you can see from the chart below, that gives the Silverado/Sierra HD an advantage in both horsepower and torque over its diesel bretheren from Ford and Dodge. (Thanks to pickuptrucks.com for the chart.) Some of the features of the new Duramax, from the official GM press release:

The more powerful 6.6L Duramax is also more fuel-efficient – up to 11-percent greater highway fuel economy than the outgoing model – reduces NOx emissions by up to 63 percent and helps enable greater towing ratings. Silverado 3500HD equipped with a fifth wheel hitch can tow up to 20,000 pounds (9,072 kg). The increased fuel efficiency, combined with a new, 36-gallon (136 L) fuel tank, provides up to 680 miles (1,090 km) of highway driving between fill-ups.

With nearly 1.3 million Duramax diesel engines put into operation since its launch in 2000, no other automaker has as much diesel engine development experience for meeting the demands of the heavy-duty truck customer

GM issued a press release not too long ago regarding the new emission control technology for their 2011 Duramax Diesel. We had a post about the new Duramax last month, so this information should clear up some of the questions we all had about the size of tank and heating system on the Urea injection.

GM’s 6.6L Duramax diesel features the latest in emission control technology, making it the cleanest Duramax engine ever produced, with NOx emissions reduced by at least 63 percent, compared to the 2010 model. NOx emissions are controlled via a Selective Catalyst Reduction aftertreatment system that uses urea-based Diesel (Emission) Exhaust Fluid (DEF). The DEF is housed in a 5.3-gallon (20 L) tank and needs to be replenished about every 5,000 miles (8,000 km). Electrically heated lines feed the DEF to the emission system to ensure adequate delivery in cold weather.

The 2011 Duramax 6.6L will also include GM’s second-generation diesel particulate filter system. Unlike most of the competition, the Duramax regenerates its diesel particulate filter using a downstream injection of diesel fuel directly into the exhaust stream and can travel up to 700 miles (1,125 km) between regenerations – a 300-mile (482 km) increase over the previous Duramax engine. The use of downstream injection also helps to improve engine life by eliminating concerns surrounding the possibility of diesel fuel contaminating engine oil, which can happen when fuel used for regeneration is introduced directly into the cylinder.

We should be receiving the new Duramax trucks in the 3rd quarter of this year – check back for any new information.

Why the need for a new round of updates to the Duramax just three years after the current engines arrived? On Jan. 1, 2010, all new diesel-powered vehicles had to meet tougher federal diesel emission standards that will reduce allowable nitrogen oxide levels by 90 percent from today, 96 percent from 1994 levels.
NOx is a major air pollutant that contributes to smog, asthma, and respiratory and heart diseases. It’s a byproduct of diesel’s high combustion temperatures.
The new Duramax diesel engines are built to meet new clean-air regulations, plus they feature other key improvements in technology and capability. Like today’s Duramax, the Isuzu-GM joint venture engine will continue to be available in two versions.

“The new Duramax diesels are based on the same engines that have been around since 2001,” said Gary Arvan, a GM diesel powertrain engineering chief. “The 2500 and 3500 Chevrolet Silverado and GMC Sierra HD pickups receive the high-power LML motor [replacing the 2007-10 LMM], while the 2500 and 3500 heavy-duty vans receive the lower-rated LGH engine [also replacing the LMM]. Both have iron blocks, aluminum cylinder heads, and their [6.6-liter] bore and stroke are unchanged.”
The LML will be paired with an Allison six-speed transmission while the LGH will be mated to GM’s in-house 6L90 six-speed gearbox, which is also matched with the 6.0-liter V-8 gas engine.

The two biggest technical changes Arvan shared details about are the Duramax’s all-new selective catalytic reduction and its enhanced exhaust gas recirculation systems — which are needed to scrub NOx down to no more than .2 grams per horsepower/hour — as well as its approved use of B20 biodiesel. That’s 80 percent ultra-low-sulfur diesel and 20 percent biodiesel.
NOx selective catalytic reduction uses diesel exhaust fluid. The urea-based solution (32.5 percent industrial urea and 67.5 percent deionized water) is held in a 5.5-gallon storage tank and injected as a fine mist into the Duramax’s hot exhaust gases. The heat turns the urea into ammonia that — when combined with a special catalytic converter — breaks the NOx down into harmless nitrogen gas and water vapor.

The exhaust fluid refill point for the HD pickups is mounted under the hood of the engine, while the vans’ is positioned next to the fuel door on the side of the vehicle. The tank is mounted on the side of the driver-side frame rail.
Arvan says diesel exhaust fluid refill intervals will vary depending on duty cycle. Some customers will only have to refill during routine maintenance, such as when the oil is changed, while others will have to top off the tank sooner.
“If they’re towing frequently, they’ll [likely] have to fill up with DEF again sooner,” Arvan said.

To ensure that the exhaust fluid tank is refilled, Duramax-equipped trucks will warn the driver when the fluid is down to a 1,000-mile range. A series of start-up warnings — including lights, chimes and messages — will become more frequent until the tank is empty. If the driver continues to operate the truck with a dry tank, after a final warning and restart the truck will only operate in a “limp-home” mode that limits speed to just 5 mph until the tank is refilled.

The selective catalytic reduction and diesel-particulate filter systems depend on a diesel oxidation catalyst that’s positioned downstream, behind the engine, to start the NOx and soot-scrubbing processes. The catalyst requires high temperatures to perform. Those temperatures are achieved on-demand by the addition of a new fuel injector that’s been positioned directly behind the exhaust outlet of the Duramax’s variable-geometry turbo instead of using the engine’s eight existing in-cylinder injectors. Fuel is squirted into the hot exhaust and burns, quickly raising temperatures in the catalysts.

The LML and LGH also make greater use of exhaust gas recirculation across the Duramax’s power band than did the LMM Duramax. The system recirculates a portion of the engine’s exhaust back into the engine at a lower temperature. The cooled gases have a higher heat capacity and contain less oxygen than air, lowering combustion temperatures and reducing the formation of NOx. Exhuast gas recirculation is prevalent in today’s clean-diesel engines to reduce NOx, but it’s not efficient enough in its current form to meet 2010 emissions levels in GM’s trucks, hence the use of selective catalytic reduction also.

Power ratings play a role in how much emissions equipment is needed.
“We’ve improved the performance of the Duramax in the van to 250 horsepower and 500 pounds-feet of torque from today’s 250 hp and 460 pounds feet,” Arvan said. “We aren’t prepared to talk about the new power figures for the heavy-duty trucks yet, but we won’t let the new emissions regulations bring us down [in power]. We’ll produce at least the 360 hp and 660 pounds-feet of torque [with the LML] that we make with today’s engine.”

We think there will be a significant power bump when the final numbers are revealed.
The LGH Duramax has a smaller exhaust gas recirculation cooler than the LML motor because of its lower power ratings. It also has a smaller radiator and cooling system.

Efficiency improvements to the recirculation system include new separate cold and hot circuits that allow exhaust gas to recirculate immediately after engine startup, when engine temperatures are still relatively cool and when the engine is idling.
In addition to burning cleaner, the LML/LGH Duramax can also burn greener. It’s certified to burn B20 biodiesel, up from the LMM’s B5 rating.
“We made a lot of enhancements to make sure the new Duramax is robust with biodiesel,” Arvan said. “The engine uses our latest-generation fuel filter that includes a coalescing filter to trap any water that could be present in the fuel. The downstream injector [behind the exhaust] for diesel particulate filter regeneration means we also won’t have a worry of oil dilution with B20 fuel from in-engine post injection [like is used on the LMM diesel]. There’s also additional heating to the fuel circuit so the filter won’t get plugged from old [B20] fuel gelling or waxing.”

Another big change to the Duramax’s fuel system is the first-time use in the Duramax of piezo electric injectors, which can react faster to fuel demands than the old solenoid injectors could. Fuel pressures are up from 1,800 bar (26,000 psi) to 2,000 bar (29,000 psi) for improved fuel atomization and combustion control. The piezo injectors run on an all-electric circuit in the engine, which helps explains the high-voltage cable we’ve seen in spy photos of the engine.
The new Duramax keeps the same Garrett-supplied single turbo setup of the LMM Duramax, though the compressor and turbine wheel diameters and blade trims have changed. The turbo also uses the same “boreless” compressor wheel.
The Duramax also continues to use a conventional gray iron engine block, but it’s been structurally enhanced around the lower skirt to help reduce noise, vibration and harshness. Combined with a new pre-combustion fuel-injection scheme that injects two pilot injections into the cylinder before the main injection, noise levels have been reduced up to 50 percent in the 1,500-1,600 rpm peak torque operating range.
“We focused on getting NVH down in the heaviest driving points,” Arvan said.
We briefly drove a 15-passenger Chevrolet Express 2500 van with the LGH Duramax diesel under its hood. While we weren’t able to do much more than a few quick starts and stops and some city-driving route simulations, we could immediately tell the engine was much quieter than the current LMM Duramax. Arvan said the van we drove was pre-production and only about three-quarters of the way through finalizing its engine calibrations.

Another change is reduced engine-idle speed. Arvan says it’s been reduced from 720 rpm to 640 rpm in the pickups. The van is able to idle at only 600 rpm.
All new engine controllers are needed to manage the sophisticated fuel and emissions system. Arvan says they have twice the number of calibrations as the previous LMM diesel to help the engine run as efficiently as possible across the widest range of operating conditions.

The oil pump is slightly bigger, plus there have been some minor changes to the crankshaft and pistons. Aluminum heads — a Duramax hallmark — remain. Engine weight is said to be comparable to the LMM engine.
Arvan also says fuel economy will remain the same — a key concern of any new diesel owner given the emphasis on clean emissions over operating efficiency.
What isn’t GM yet sharing about the 2011 Duramax? We still don’t know final power ratings for the HD pickups, and there are still a few surprises for a later date — like perhaps an integrated exhaust brake.
“We’re working on some things in that area [exhaust brake integration],” Arvan said. “We’ll see. It’s part of future discussions.”

We’re definitely looking forward to getting the new Duramax trucks and getting to see this new technology for ourselves.